this is java code

@Data
public class UserBaseVo {
    @NotNull
    @Length(min = 6, max = 12)
    private String username;
    @NotNull
    @Min(0)
    @Max(1)
    private Integer sex;
    @NotNull
    @Min(0)
    @Max(1)
    private Integer status;
}

@EqualsAndHashCode(callSuper = true)
@Data
public class UserUpdateVo extends UserBaseVo {
    @NotNull
    private Long id;
}

@RestController
public class UserController {
    @PostMapping("create")
    public Res<Boolean> createUser(@RequestBody @Valid UserBaseVo baseVo) {
        //service.create
        return ok(true);
    }

    @PostMapping("update")
    public Res<Boolean> updateUser(@RequestBody @Valid UserUpdateVo updateVo) {
        //service.create
        return ok(true);
    }
}

This way I can verify different objects when I create and modify the user. The code is simple. But kotlin can’t be done as succinctly as this. Look at the kotlin code

// method 1
KtUserUpdateVo
open class KtUserBaseVo(
    @Length(min = 6, max = 12)
    var username: String,
    @Min(0)
    @Max(1)
    var sex: Int,
    @Min(0)
    @Max(1)
    var status: Int,
)

class KtUserUpdateVo(var id: Long, username: String, sex: Int, status: Int) : KtUserBaseVo(username, sex, status)

// method 2
open class KtUserBaseVo {
    @NotNull
    @Length(min = 6, max = 12)
    var username: String? = null

    @NotNull
    @Min(0)
    @Max(1)
    var sex: Int? = null

    @NotNull
    @Min(0)
    @Max(1)
    var status: Int? = null
}

class KtUserUpdateVo : KtUserBaseVo() {
    @NotNull
    var id: Long? = null
}

method 1: This approach defines redundant fields in the construction of
method 2: This approach defines unnecessary nullable types because none of them can be nullable, thus losing kotlin’s non-nullable nature

kotlin both of these methods have shortcomings, do you have any better solutions, thank you very much